Concurrent Sessions B: Fish Physiology and Fishway Passage Success - Using Accelerometer Transmitters to Examine the Activity and Swimming Behaviour of Adult Sockeye Salmon During Dam Passage

Flow manipulation and fragmentation through hydropower development often obstructs the dispersal and migration of organisms, potentially causing changes in fish habitat, population sizes, community structure and ecosystem function. Indeed, human-caused alterations to river systems are of greater concern to semelparous fish (e.g., Pacific salmon Oncorhynchyus spp.) that are limited to asingle opportunity to reproduce and contribute to future generations on a fixed energy budget. Complex hydrodynamics and turbulence downstream of hydropower facilities have been known to act as bottlenecks to migration and cause confusion in adult salmonids, resulting in delays ranging from several hours to days. To date, little is known about what constitutes a biologically relevant delay in which there are individual level fitness consequences. Building on a previous dataset, we examined the activity, behaviour and energetics of sockeye salmon (O. nerka) in relation to the operational regime of the Seton Dam in southwestern British Columbia, Canada. Adult sockeye were tagged with tri-axial acoustic accelerometers to enable the remote observation of fine-scale movement and energy use in the wild; data from these tags can be used as a proxy for swimming speed and thus be used to estimate energy expenditure. Our analyses were focused on the predictors of and mechanisms behind passage success or failure. Fish that delayed longer within the dam tailrace were less likely to successfully pass the dam, and surprisingly, successful migrants crossed the turbulent tailrace area multiple times in order to locate, enter and ascend the Seton Dam fishway. As expected, our results support previous work in that females have a lower passage success rate compared to males, particularly during periods of high dam-spill discharge. Results will be discussed in the context of the long-standing management question of whether hydropower-related delays in migration influence energy use and passage success